Method and apparatus for supporting cables within coil tubing

ABSTRACT

A method of hanging a cable within a coiled tubing string includes the steps of determining a length of coiled tubing required within a well having a wellhead; determining a length of a cable required within the coiled tubing, the cable having a structural component along the length of the cable sufficient to support the weight of the cable; cutting the tubing string and installing a hanger sub in the coiled tubing string toward the wellhead attachment section relative to the downhole end, the hanger sub comprising an inner shoulder that extends radially into the hanger sub and defines an opening; and attaching an outer shoulder to the cable and inserting the cable into the coiled tubing string until the outer shoulder of the cable engages the inner shoulder of the hanger sub such that the inner shoulder positions the cable below the outer shoulder.

FIELD

This relates to a method and apparatus for supporting cables withincoiled tubing.

BACKGROUND

Coiled tubing has become a more common element for use in downholeoperations, and may be used to house cables, such as, supply lines,capillary tubing, and the like. U.S. Pat. No. 6,352,113 (Neuroth),entitled “Method and apparatus to remove coiled tubing deployedequipment in high sand applications” and U.S. Pat. No. 6,143,988(Neuroth et al.), entitled “Coiled tubing supported electrical cablehaving indentations” each describe different supports used to support acable within the coiled tubing.

SUMMARY

According to an aspect, there is provided a method of hanging a cablewithin a coiled tubing string. The cable has a first end and a secondend. The method comprises the steps of providing a coiled tubing stringhaving a length required within a well having a wellhead, the coiledtubing having a wellhead attachment section and a downhole end spacedfrom the wellhead attachment section; determining a length of a cablerequired within the coiled tubing string, the cable comprising anelongate structural component that extends along the length of thecable, the structural component being sufficient to independentlysupport the weight of the cable; cutting the coiled tubing string intofirst and second sections and installing a hanger sub in the coiledtubing string between the first and second sections toward the wellheadattachment section relative to the downhole end, the hanger subcomprising an inner shoulder that extends radially into the hanger suband defines an opening; attaching an outer shoulder to the elongatestructural component of the cable and inserting the cable into thecoiled tubing string until the outer shoulder engages the inner shoulderof the hanger sub such that the cable is hanging within the coiledtubing string below the inner shoulder; and installing the coiled tubingstring in a wellhead such that the wellhead attachment section isadjacent to the wellhead and the hanger sub is below the wellhead.

According to another aspect, the hanger sub may be attached to thecoiled tubing such that the outer profile is in line with the outerprofile of the coiled tubing

According to another aspect, the cable may comprise a supply line.

According to another aspect, the method may further comprise the step ofattaching the second end of the cable to a downhole tool. The downholetool may be an electric submersible pump.

According to another aspect, the structural component may comprise ametal capillary tube.

According to another aspect, the cable may comprise a bundle of supplylines. The hanger sub may comprise two or more apertures, at least oneaperture comprising the inner shoulder that engages the elongatestructural component, at least a portion of the bundle of supply linespassing through a separate aperture, the elongate structural componentstructurally engaging the supply lines below the hanger sub. Theelongate structural component may comprise a metal capillary tube in thebundle of supply lines.

According to another aspect, the cable may comprise a resistive heatingelement.

According to another aspect, the hanger sub in the coiled tubing stringmay be between 1 and 50 meters below the wellhead when installed, orbetween 5 m and 25 m below the wellhead when installed.

According to another aspect, the hanger sub in the coiled tubing stringmay be positioned below the wellhead end of the coiled tubing string ata depth of between 1% and 5% of the wellbore depth.

According to another aspect, at least one of the shoulder of the hangersub and the shoulder on the cable may be slotted to prevent rotation ofthe cable.

According to another aspect, the weight of the cable may be supportedsolely by the hanger sub.

According to an aspect, there may be provided, in combination, a cableand a length of coiled tubing string. The cable has a first end and asecond end and comprises a structural component along the length of thecable. The structural component is sufficient to support the weight ofthe cable. The length of coiled tubing string has a wellhead end and adownhole end. The coiled tubing string has a first section and a secondsection connected by a hanger sub. The hanger sub comprises an innershoulder that extends radially into the hanger sub and defines anopening. The cable has an outer shoulder capable of engaging the innershoulder of the hanger sub, such that, when installed through awellhead, the hanger sub is positioned below the wellhead.

According to another aspect, the outer profile of the hanger sub may bein line with the outer profile of the coiled tubing

According to another aspect, the cable may comprise a supply line.

According to another aspect, the second end of the cable may have adownhole tool attached. The downhole tool may be an electric submersiblepump.

According to another aspect, the structural component may comprise ametal capillary tube.

According to another aspect, the cable may comprise a bundle of supplylines. The hanger sub may comprises two or more apertures, at least oneaperture comprising the inner shoulder that engages the elongatestructural component, at least a portion of the bundle of supply linespassing through a separate aperture, the elongate structural componentstructurally engaging the supply lines below the hanger sub. At leastone supply line may comprise a metal capillary tube, the metal capillarytube providing structural support to the supply lines.

According to another aspect, the cable may comprise a resistive heatingelement.

According to another aspect, the hanger sub may be installed at adistance of between 1 and 50 meters from the wellhead end, or at adistance of between 5 and 25 m from the wellhead end.

According to another aspect, the hanger sub in the coiled tubing stringmay be positioned below the wellhead end of the coiled tubing string ata depth of between 1% and 5% of the wellbore depth.

According to another aspect, at least one of the shoulder of the hangersub and the shoulder on the cable may be slotted to prevent rotation ofthe cable.

According to another aspect, the weight of the cable may be supportedsolely by the hanger sub when installed in the wellhead.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become more apparent from the followingdescription in which reference is made to the appended drawings, thedrawings are for the purpose of illustration only and are not intendedto be in any way limiting, wherein:

FIG. 1 is a side elevation view in section of a supply line hanging in acoiled tubing string.

FIG. 2 is a top view of a hanger sub.

FIG. 3 is a top view of a hanger sub in a particular embodiment.

FIG. 4 is a side elevation view of a hanger sub.

FIG. 5 is a side elevation view of an apparatus for servicing anelectric submersible pump.

FIG. 6 is a side elevation view of a well completion with an electricsubmersible pump connected to surface by a coiled tubing string andelongate supply lines within the coiled tubing string.

DETAILED DESCRIPTION

An apparatus and method of positioning a cable within a coiled tubingstring will be described with reference to FIGS. 1-6 in the context ofan electric submersible pump in a well with a positive well headpressure. It will be understood that the support described below mayalso be used in other situations as well.

Referring to FIG. 6, well 12, which may be a pressurized well, includesa casing 14 and a wellhead 16 mounted to casing 14. Wellhead 16 has asealable injection port 18, and production ports 20. Referring to FIG.5, injection port 18 may be sealed by a blow out preventer (BOP) 32 asshown, or it may also be sealed by a valve, a plug, etc., which may beabove or below the actual port 18. Referring again to FIG. 6, the numberof production ports 20 may vary depending upon the design of wellhead16. Production tubing 22 is positioned in casing 14 and is connected towellhead 16. Production fluids that are pumped upward by electricsubmersible pump 10 flow through production tubing 22 and out productionports 20 of wellhead 16. Electric submersible pump 10 is carried by acoiled tubing string 24 at a downhole end 26 of coiled tubing string 24,and is sized such that it is able to be run through production tubing22. Cables, which may include a metal capillary tube 28 and other supplylines 29 as shown in FIG. 1, are run through and enclosed within coiledtubing string 24 and connect to electric submersible pump 10. Metalcapillary tube 28 is preferably used to supply oil, while other supplylines 29 may be used for power, communication lines, control lines,instrumentation lines, resistive heating elements, and the like. Thechoice of cable may be such that the cable is structurallyself-supporting. Alternatively, metal capillary tube 28 providesstructural support to supply lines 29. A pump-receiving housing 30,shown in FIG. 5, is located above injection port 18 of wellhead 16. Theheight of pump receiving housing 30 will depend upon the size ofelectric submersible pump 10. Pump-receiving housing 30 is designed suchthat it may be sealed to the atmosphere when injection port 18 is open,and openable to the atmosphere when injection port 18 is sealed. Inother words, housing 30 works with injection port 18 to ensure that well12 is always sealed when it is pressurized. Referring to FIG. 5, a BOP32 is located above wellhead 16 and below pump-receiving housing 30.Coiled tubing injector 34 is located above pump-receiving housing 30and, referring to FIG. 6, is used to control the position of coiledtubing string 24 and electric submersible pump 10 in well 12.

Referring to FIG. 1, metal capillary tube 28 provides structural supportto supply lines 29. As shown, this is done by attaching supply lines 29to capillary tube 28 using clamps 31, although it may also be done inother ways. For example, supply lines 29 and capillary tube 28 may beencapsulated together. Furthermore, supply lines 29 and capillary tube28 may be any self-supporting cable that acts as a structural componentand that may be used in downhole applications.

As shown, supply lines 29 generally require structural support as thelengths of tube 28 and lines 29 may be long enough to overcome theinherent strength of lines 29 and stretch or break. Once supply lines 29are supported by capillary tube 28 they become self-supporting.Capillary tube 28 and supply lines 29 are mounted within and supportedby coiled tubing string 24. This is done by providing coiled tubingstring 24 with a hanger sub 102 that has a shoulder 104 that engages acorresponding shoulder 106 carried by capillary tube 28. Hanger sub 102is preferably close to surface 108, such as between 1 meter and 50meters below surface, such that the majority of the length of capillarytube 28 is below hanger sub 102 and coiled tubing string 24 and therewill not be movement at the surface where there is required an anchorpoint. Alternatively, capillary tube 28 may be mounted at a positionthat is based on a percentage of the depth of the wellbore, such asbetween 1% and 5%. Hanger sub 102 is preferably a single body but may bea two-piece that can be placed around supply lines 29. As shown, thehanger sub shoulder is integrally formed with the hanger sub. The hangersub is welded or otherwise attached to the coiled tubing such that theouter profile is in line with the outer profile of the coiled tubing.This ensures that the coiled tubing does not have an external upset orany increased outer diameter, which allows for ease of transport andinstallation. The hanger sub is attached by welding or another method insuch a way that it does not substantially degrade the mechanicalproperties of the coiled tubing and has properties that are within thespecifications for the coiled tubing string as a whole. This isparticularly useful in thermal applications, where the propertiesincluding resistance to corrosion are maintained within thespecifications required for the coiled tubing.

Referring to FIGS. 2 and 4, hanger sub 102 has an opening 110 throughwhich the cable will pass. The shoulder 106 attached to the cable willengage hanger sub shoulder 104, positioning the cable within the hangersub 102.

Referring to FIG. 3, in a particular embodiment, hanger sub shoulder 104may have an additional opening 112 that provides a passage for anadditional support cable if needed. In this embodiment the cable mayhave a support line such as a capillary support tube, metal wire, orrod, attached to the cable to provide structural support below thehanger sub. The support line may carry the shoulder 106 which ispositioned above opening 112, shoulder 106 engaging with hanger subshoulder 104 at opening 112.

Referring to FIG. 4, hanger sub 102 is shown from a side elevation.

The description above assumes a situation where both power orcommunication and fluid supply are connected to a downhole tool.However, this may change depending on the circumstances. For example,rather than a bundle of supply lines 28 and 29, in some circumstancesthere may only be a metal capillary tube 28, or more than one capillarytube 28. In other circumstances, there may not be a capillary tube 28.While a metal capillary tube 28 is useful for providing structuralsupport, other structural members may also be provided if fluid is notrequired downhole, such as a metal wire or rod that are less expensivethan capillary tube 28.

When one hanger sub 102 is provided, capillary tube 28 may be run in tocoiled tubing string 24 without any other hindrance, and will beproperly positioned once it is correctly inserted without taking anyadditional steps in the process. By knowing the length of coiled tubingstring 24 and the length of capillary tube 28, hanger sub 102 and outershoulder 106 may be installed to have each end at the correct position,such as to attached to an electric submersible pump 10 as shown in FIG.6, or any other downhole tool that may be run on a coiled tubing string.

The above structure may be used when installing or removing an electricsubmersible pump 10 without having to cool well 12. In the depictedexample, in order to insert electric submersible pump 10 into a wellwith a positive well head pressure, injection port 18 is first sealed byclosing BOP 32. Pump-receiving housing 30 contains electric submersiblepump (ESP) 10, which is then connected to coiled tubing string 24. Pumpreceiving housing 30 is then mounted to the BOP 32. Pump-receivinghousing 30 is then closed and sealed to atmosphere and BOP 32 is openedto allow electric submersible pump 10 to be inserted through injectionport 18 in wellhead 16 and into well 12 by operating coiled tubinginjector 34. In order to remove electric submersible pump 10 frompressurized well 10, the process is reversed, with coiled tubinginjector 34 lifting electric submersible pump 10 through wellhead 16 andinto housing 30. BOP 32 is then closed and sealed, and housing 30 iseither opened or removed from BOP 32 to provide access to electricsubmersible pump 10. Electric submersible pump 10 may then be servicedor replaced, as necessary.

As depicted, electric submersible pump 10 is preferably an invertedelectric submersible pump, and is run off a 1¼″-3½″ coiled tubing string24 that contains the instrumentation lines. Other sizes may also beused, depending on the preferences of the user and the requirements ofthe well. When compared with traditional electric submersible pumps,electric submersible pump 10 lacks the seal section, motor pothead andwellhead feedthrough. As shown, electric submersible pump 10 includes apower head 27, motor section 38, thrust chamber 40, one or more sealrings 42 and electric submersible pump section 44. Thrust chamber 40includes two mechanical seals with a check valve (not shown), andreplaces the conventional seal/protector section that separates pumpsection 44 and motor section 38. The check valve in thrust chamber 40allows the lubricating fluid supplied by capillary tube 28 to exitthrust chamber 40 and comingle with, for example, produced fluids fromthe well with the pump discharge from outlet ports 50. Seal rings 42seal against a pressure sealing seat 46 that is carried by productiontubing 22, to provide seal between inlet ports 48 and outlet ports 50.Inlet ports 48 are in communication with downhole fluids to be pumped tosurface via outlet ports 50, which are positioned within productiontubing 22.

In this patent document, the word “comprising” is used in itsnon-limiting sense to mean that items following the word are included,but items not specifically mentioned are not excluded. A reference to anelement by the indefinite article “a” does not exclude the possibilitythat more than one of the element is present, unless the context clearlyrequires that there be one and only one of the elements.

The following claims are to be understood to include what isspecifically illustrated and described above, what is conceptuallyequivalent, and what can be obviously substituted. Those skilled in theart will appreciate that various adaptations and modifications of thedescribed embodiments can be configured without departing from the scopeof the claims. The illustrated embodiments have been set forth only asexamples and should not be taken as limiting the invention. It is to beunderstood that, within the scope of the following claims, the inventionmay be practiced other than as specifically illustrated and described.

What is claimed is:
 1. In combination: a cable having a first end and asecond end, the cable comprising an elongate structural component alongthe length of the cable, the structural component being sufficient tosupport the weight of the cable, the cable comprising a bundle ofcontinuous supply lines; and a length of coiled tubing string having awellhead end and a downhole end, the coiled tubing string having a firstsection and a second section connected by a hanger sub, the hanger subdefining a central bore and comprising an inner shoulder that extendsradially into the central bore of the hanger sub, the cable having anouter shoulder capable of engaging the inner shoulder of the hanger sub,such that; wherein the hanger sub comprises two or more apertures, atleast one aperture comprising the inner shoulder that engages theelongate structural component, at least a portion of the bundle ofcontinuous supply lines passing through a separate aperture of the twoor more apertures, the elongate structural component structurallyengaging the supply lines below the hanger sub.
 2. The combination ofclaim 1, wherein the outer profile of the hanger sub is in line with theouter profile of the coiled tubing string.
 3. The combination of claim1, wherein the cable comprises a supply line.
 4. The combination ofclaim 1, wherein the second end of the cable has a downhole toolattached.
 5. The combination of claim 4, wherein the downhole tool is anelectric submersible pump.
 6. The combination of claim 1, wherein thestructural component comprises a metal capillary tube.
 7. Thecombination of claim 1, wherein at least one supply line from the bundleof continuous supply lines comprises a metal capillary tube, the metalcapillary tube providing structural support to the supply lines.
 8. Thecombination of claim 1, wherein the cable comprises a resistive heatingelement.
 9. The combination of claim 1, wherein the hanger sub isinstalled at a distance of between 1 and 50 meters from the wellheadend.
 10. The combination of claim 1, wherein the hanger sub in thecoiled tubing string is at a distance of between 5 and 25 meters fromthe wellhead end.
 11. The combination of claim 1, wherein the hanger subin the coiled tubing string is positioned below the wellhead end of thecoiled tubing string at a depth of between 1% and 5% of the wellboredepth.
 12. The combination of claim 1, wherein at least one of the innershoulder of the hanger sub and the outer shoulder of the cable areslotted to prevent rotation of the cable.
 13. The combination of claim1, wherein the weight of the cable is supported solely by the hanger subwhen installed in the wellhead.
 14. The combination of claim 1, wherein,when the coiled tubing string is installed through a wellhead, thehanger sub is positioned below the wellhead.
 15. The combination ofclaim 1, wherein, when the coiled tubing string is installed through awellhead, a majority of the cable is below the hanger sub.
 16. Incombination: a cable having a first end and a second end, the cablecomprising a structural component along the length of the cable, thestructural component being sufficient to support the weight of thecable; and a length of coiled tubing string having a wellhead end and adownhole end, the coiled tubing string having a first section and asecond section connected by a hanger sub, the hanger sub defining acentral bore and comprising an inner shoulder that extends radially intothe central bore of the hanger sub, the cable having an outer shouldercapable of engaging the inner shoulder of the hanger sub; wherein thehanger sub in the coiled tubing string is positioned below the wellheadend of the coiled tubing string at a depth of between 1% and 5% of thewellbore depth.
 17. The combination of claim 16, wherein the cablecomprises a resistive heating element.
 18. The combination of claim 16,wherein, when the coiled tubing string is installed through a wellhead,the hanger sub is positioned below the wellhead.
 19. The combination ofclaim 1, wherein, when the coiled tubing string is installed through awellhead, a majority of the cable is below the hanger sub.